In a folder the sheet abutments and guides must be set to the size of the respective sheet to be folder at the start of a run. The setting up of a new run is, however, a very slow process. Depending upon the speed of the conveyor tapes, the controller of the folder must determine when the conveying means must be switched off (i.e., at an earlier or later point in time) if the sheets being supplied to the folder are to come to rest at the correct position underneath the chopper in order to perform adjustment of the abutments and guides.